acre = 4,840 square yards (0.405 hectare).
From Old English (denoting the ammount of land a yoke of oxen could plough in a day).
Of German origin; related to Dutch akker and German Acker 'field', from an Indo-European root shared by Sanskrit ajra 'field', Latin ager, and Greek agros.rood = a quarter of an acre ; (40 square perches, aprox. 0.1012 hectare).
Old English rod, related to Dutch roede, and German Rute 'rod'.perch = a quarter of a chain or 5 1/2 yards (aprox. 5.029metres). Also called Pole, Rod.